Multiple photos libraries in icloud

I created a new photos library(2) and chose it to be the system photo library. I imported the pictures I wanted and let them all upload to icloud as I chose to use icloud photos. I still have my original library(1) on my iMac in my PICTURES folder. I make the assumption that the ONLY photos in icloud are those from the NEW library(2) I created. Today I started photos with the option key and chose to use the ORIGINAL library(1). After some time rebuilding, photos opened and all my original photos, albums, etc were there. I assume that these photos, etc are NOT in icloud, but only on my iMac hdd. Is that correct?

If I now choose to make this original library the system library, will all the pics etc showing with the original library(1) now be uploaded to icloud while the photos from the library(2) be deleted?

Will the photos etc from library(2), even though not the system library, remain on my iMac hdd?

I apologize in advance if I am asking questions that are easily answered with a quick google search, but I've had too much wrong info and wanted to check with pros.